The candidate field for next year’s mayoral election just got a little smaller.

What’s that?

You didn’t know there was a candidate field for next year’s mayoral election — or, for that matter, that Mayor Bloomberg’s 12-year City Hall tenure expires at the end of 2013?

Well, that’s understandable.

You probably have a life.

So you probably also didn’t notice that Scott Stringer, the Manhattan borough president, abandoned his formally unannounced candidacy for mayor — by all accounts to run for city comptroller, but only if the incumbent, John Liu, attaches his wagon-full of legal woes to a mayoral candidacy of his own.

Zany stuff, New York politics — one year out, nobody seems to care but the commentariat, which is obsessed. (What does that make us, huh?)

Stringer’s putative mayoral run had barely registered on anyone — which is pretty much why he decided to hitch his star to Liu’s future (which is really bizarre).

So suddenly there were four: Liu, Council Speaker Christine Quinn, Public Advocate Bill de Blasio and ex-Comptroller Bill Thompson.

These folks are no doubt very nice to children and small animals — but none has a résumé that suggests qualification for an office higher than the one already held (and in Liu’s case, he’s pretty much demonstrated that he’s not remotely up to the demands of the one he’s got). Which is why New Yorkers should be looking at this race with more than a little apprehension.

Now, we’ve generally been supportive — despite some differences over the years — of Bloomberg as well as his predecessor, Rudy Giuliani. But there’s no denying that the pair, in their collective two decades at the City Hall helm, have shown leadership that’s been dynamic, often visionary and clearly up to the demands of a complex and — in many ways — very troubled city.

No reasonable person would deny that New York is a far better place to live and work — on just about every level — than it was at the close of the David Dinkins era, 20 years ago.

Both men, in their respective ways and at a comparable point in the campaign, articulated compelling arguments in their own behalf.

The best that can be said of the Gang of Four, up to this point, is that it seems to have a pulse, and that it’s hard at work writing chits — if not yet checks — to the various special interests that have pretty much been in the wilderness for 20 years. (Right, Mike Mulgrew: We’re looking straight at you.)

Next year’s contest is shaping up to be a crossroads election — one that could decide New York’s course for a generation.